The present invention relates to hydraulic cylinders and pistons, in general, and more particularly to hydraulic cylinders having their internal surface and pistons having their external surface treated such as to provide a wear resistant low friction surface, and to the method of obtaining such a surface.
The present invention has general applications to a variety of hydraulic cylinders and pistons, and more particularly it has particular applications to hydraulic slave and master cylinders as used in hydraulic brake systems and clutch hydraulic control systems of motor vehicles.
It is important that hydraulic cylinders be resistant to wear while at the same time causing no undue wear on piston seals, and that sliding friction or resistance between piston seals and cylinder walls be substantially low, for reducing hysteresis, vibration and noise, such as high frequency noise or squeak, without loss of sealing characteristics, more particularly in master cylinders. Secondarily, it is advantageous to have the surface of pistons provided with a coating which has a low coefficient of friction, especially at areas which may occasionally engage with areas of the associated cylinder wall.